Re: [PATCH] arch/m68k/kernel/sys_m68k: Add missing mmap_read_lock() to sys_cacheflush()

[Geert Uytterhoeven]

On Wed, Apr 7, 2021 at 10:00 PM Liam Howlett  wrote:
> When the superuser flushes the entire cache, the mmap_read_lock() is not
> taken, but mmap_read_unlock() is called.  Add the missing
> mmap_read_lock() call.
>
> Signed-off-by: Liam R. Howlett 

Reviewed-by: Geert Uytterhoeven 
i.e. will queue in the m68k for-v5.13 branch.

Gr{oetje,eeting}s,

Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- ge...@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds

Re: [PATCH] arch/m68k/kernel/sys_m68k: Add missing mmap_read_lock() to sys_cacheflush()

[Matthew Wilcox]

On Thu, Apr 08, 2021 at 04:34:20PM +, Liam Howlett wrote:
> When the superuser flushes the entire cache, the mmap_read_lock() is not
> taken, but mmap_read_unlock() is called.  Add the missing
> mmap_read_lock() call.
> 
> Fixes: cd2567b6850b (m68k: call find_vma with the mmap_sem held in
> sys_cacheflush())
> Signed-off-by: Liam R. Howlett 

Reviewed-by: Matthew Wilcox (Oracle) 

Although if it's been broken since 2014, maybe the ability of the
superuser to flush the entire cache is not needed any more and can
be removed?

Re: [PATCH] arch/m68k/kernel/sys_m68k: Add missing mmap_read_lock() to sys_cacheflush()

[Liam Howlett]

Forgot the fixes line.

* Liam Howlett  [210407 16:00]:
> When the superuser flushes the entire cache, the mmap_read_lock() is not
> taken, but mmap_read_unlock() is called.  Add the missing
> mmap_read_lock() call.
> 
> Signed-off-by: Liam R. Howlett 
> ---
>  arch/m68k/kernel/sys_m68k.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/arch/m68k/kernel/sys_m68k.c b/arch/m68k/kernel/sys_m68k.c
> index 1c235d8f53f3..f55bdcb8e4f1 100644
> --- a/arch/m68k/kernel/sys_m68k.c
> +++ b/arch/m68k/kernel/sys_m68k.c
> @@ -388,6 +388,8 @@ sys_cacheflush (unsigned long addr, int scope, int cache, 
> unsigned long len)
>   ret = -EPERM;
>   if (!capable(CAP_SYS_ADMIN))
>   goto out;
> +
> + mmap_read_lock(current->mm);
>   } else {
>   struct vm_area_struct *vma;
>  
> -- 
> 2.30.0
From aeee71b15f54426f02f41a4408afbd0b5acab7ec Mon Sep 17 00:00:00 2001
From: "Liam R. Howlett" 
Date: Wed, 7 Apr 2021 11:39:06 -0400
Subject: [PATCH] arch/m68k/kernel/sys_m68k: Add missing mmap_read_lock() to
 sys_cacheflush()

When the superuser flushes the entire cache, the mmap_read_lock() is not
taken, but mmap_read_unlock() is called.  Add the missing
mmap_read_lock() call.

Fixes: cd2567b6850b (m68k: call find_vma with the mmap_sem held in
sys_cacheflush())
Signed-off-by: Liam R. Howlett 
---
 arch/m68k/kernel/sys_m68k.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/arch/m68k/kernel/sys_m68k.c b/arch/m68k/kernel/sys_m68k.c
index 1c235d8f53f3..f55bdcb8e4f1 100644
--- a/arch/m68k/kernel/sys_m68k.c
+++ b/arch/m68k/kernel/sys_m68k.c
@@ -388,6 +388,8 @@ sys_cacheflush (unsigned long addr, int scope, int cache, unsigned long len)
 		ret = -EPERM;
 		if (!capable(CAP_SYS_ADMIN))
 			goto out;
+
+		mmap_read_lock(current->mm);
 	} else {
 		struct vm_area_struct *vma;
 
-- 
2.30.0

[PATCH] arch/m68k/kernel/sys_m68k: Add missing mmap_read_lock() to sys_cacheflush()

[Liam Howlett]

When the superuser flushes the entire cache, the mmap_read_lock() is not
taken, but mmap_read_unlock() is called.  Add the missing
mmap_read_lock() call.

Signed-off-by: Liam R. Howlett 
---
 arch/m68k/kernel/sys_m68k.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/arch/m68k/kernel/sys_m68k.c b/arch/m68k/kernel/sys_m68k.c
index 1c235d8f53f3..f55bdcb8e4f1 100644
--- a/arch/m68k/kernel/sys_m68k.c
+++ b/arch/m68k/kernel/sys_m68k.c
@@ -388,6 +388,8 @@ sys_cacheflush (unsigned long addr, int scope, int cache, 
unsigned long len)
ret = -EPERM;
if (!capable(CAP_SYS_ADMIN))
goto out;
+
+   mmap_read_lock(current->mm);
} else {
struct vm_area_struct *vma;
 
-- 
2.30.0